Toso or Faim3 (Fas Apoptotic inducing molecule 3) is a single membrane spanning cell surface receptor originally characterized through a retroviral overexpression screen in Jurkat cells, a T cell leukemic line, as a mediator of Fas-induced apoptotic cell death (Hitoshi, Y., et al., Toso, a cell surface, specific regulator of Fas-induced apoptosis in T cells. Immunity, 1998. 8(4): p. 461-71). Subsequent studies have suggested that Toso is the elusive receptor for IgM. The expression of Toso also seems to correlate with particularly aggressive forms of Chronic Lymphocytic Leukemia, or CLL.
There is a need for characterization of the in vivo role of Toso in order to identify its use as a therapeutic target and for compositions comprising agents that can bind to Toso and/or modulate its activity.